1. Field of the Invention
The present invention relates to playing cards that are provided with a machine-readable code. Such cards are used in connection with bridge, for instance.
2. Description of the Related Art
In certain situations there is a need to monitor card distribution. For instance, casinos need to be able to register events taking place at the gaming tables, in order to reduce the risk of fraud. In the case of bridge competitions, it is normal to duplicate card distributions, i.e. the hands dealt, so as to enable all players to play the same hands. By solely comparing the players that have played the same cards, the risk that the competition will be concerned only with the best cards that are dealt is eliminated.
It is known to provide playing cards with a machine-readable code to this end, so as to enable the various cards to be distinguished from each other and mutually identified. Also known to the art are devices that register cards taken from a pack and dealt to a player, as are also devices which divide a pack into four predetermined hands and the cards scanned mechanically and divided into four piles on the basis of the scan.
In order to widen the use of encoded playing cards there is required a simple code on the one hand and simple and inexpensive card reading devices on the other hand.
A known encoding technique involves providing the cards with a number of light dots and dark dots which lie along a line on a card, and using a reader in the form of an array of light-sensitive elements to detect the dark and light regions, respectively, as the card passes the reader. The code is fed perpendicularly to its longitudinal extension, in over the array of elements, said array extending parallel with the longitudinal extension of the code. Although this encoding and reading technique is inexpensive, it has the serious drawback that the reader, which is fixedly mounted, is unable to read a code that is displaced laterally relative to the reader as the code is advanced. This displacement, or offset, may be due to the code having been placed in the wrong position on the cards, or may be due to mechanical deficiencies in the feed mechanism by means of which the cards are mechanically discharged or sorted.
Another encoding system is one in which the cards are provided with an EAN bar code. An BAN code is normally scanned by a code reader that includes a plurality of laser beams. Although the code is read reliably, irrespective of whether it is stationary Or moves relative to the reader, the reading equipment is so expensive as to prevent its general use in the present context.
EAN codes are based on a plurality of parallel bars of different thicknesses. One inexpensive method of reading such a code, is to pass the code over a dot reader perpendicularly to the longitudinal extension of the bar code. One condition in this respect, however, is that the code is advanced past the reader at a constant speed. This is difficult to achieve. In the case of mechanical card feeders, the speed at which the cards pass the reader is liable to vary and therewith result in the code being read incorrectly. In the case of certain known card dispensing devices, the cards are withdrawn manually from a container and variations in speed are so high that known reading techniques are unable to function satisfactorily.
In summary, it can be said that there is no technique of reading a code on a playing card that moves relative to a reader in a direction where variations in the location of the code on the cards or variations in the rate at which the cards are read can be accepted.
This problem is solved by the present invention, which provides a code that can be easily read with great reliability by means of inexpensive equipment.
Accordingly, the present invention relates to playing cards that are provided with a machine-readable bar code in the form of a plurality of mutually parallel and juxtaposed bars that are intended to be scanned by means of light sensitive detectors. Each playing card is provided with at least a six-position binary code where a bar is either present of absent at each position. The code is expanded with a reference code in the form of a bar in at least one further position on one side of said binary code. The reference code is detected by a light sensitive detector, and said binary code is scanned by said light sensitive detectors when the reference code is detected.